Magnetic disk drives used for storing data, as used with computers for example, have been steadily reduced in size now that the 3.5 inch diameter floppy diskettes are widely utilized in personal computers, and the 2.5 inch hard disk drives are utilized in laptop and portable computers. Impetus for the height reduction comes from the lack of available space for larger drives, particularly in laptop and other small lightweight computers. With a desire for additional reduction of the hard disk to a diameter of approximately 1.8 inches, there is a commensurate effort to significantly reduce the thickness or height of the disk drive mechanism from approximately 10 millimeters dimension to approximately 5 millimeters.
Conventional construction of disk drives has utilized an electronic circuit board to support the electronic components necessary for control and operation of the disk drive and the related conventional function of recording data on magnetic media, as well as a rigid metal base plate for stability. The rigid metal base plate has been essential to the requirement that close control of the position of the magnetic head relative to the rotating disk to be precisely maintained. In order to prevent relative movement between the disk spindle and the axis of an actuator mechanism which positions the magnetic heads at varying positions relative to the disk surface, rigidity is essential. In order to provide a fixed datum from which the magnetic heads may be controlled for reading and writing of the data on the disk surface, the rigid base plate must maintain the orientation and spacing of the spindle and the actuator mechanism axis.
So that the head will not contact or impact the surface of the disk and thereby damage either the magnetic head or the disk during operation, any minute movement of the actuator mechanism support must be severely restricted relative to the spindle. This restriction is essential to maintain the extremely small gaps between the magnetic head and the disk surface in the order of a few microns.
Additionally, it is vital to maintain the extremely fine positioning between the magnetic head and the surface of the disk during operation. This fine positioning insures that the magnetic head remains at the necessary distance from the surface of the disk to read or write the data either from or to the magnetic media which is carried on the surface of the disk.
Reduction of the height of the disk drive enabling it to fit within the area normally used for memory cards, dictates the thickness of the various structural members of the disk drive can be reduced. The thickness of the components of the disk drive only may be reduced to a certain extent before the integrity of the component is lost. For example, the base plate must have a minimum thickness to remain sufficiently rigid. Techniques such as bending, forming or creasing the metal sheet add thickness to the part; this limits if not totally defeats, the effort to reduce part thickness of the part and/or disk drive height.
Conventional disk drives with the rigid metal base plate and the separate electronics board necessitate consumption of substantial height. When the electronics board and rigid metal base plate member are sandwiched closely together, the electronics will tend to warm the base plate and cause thermal expansion of the metal, possibly sufficient to warp or to deflect the rigid metal base plate; this warping will thus affect the spatial relationship of the actuator and the drive spindle thereby causing the magnetic heads to vary from their normal fly height. This variance either may displace the heads too far from the magnetic surface of the disk reliably to produce and/or reproduce stored data or places the magnetic heads too close to the disk surface and thus may cause the magnetic heads to contact or impact the moving disk surface, thus destroying a portion of the magnetic surface and data recorded thereon.
U.S. Pat. No. 5,025,336 to Morehouse et al., shows a stacked arrangement where the circuit board and base plate are arranged in face-to-face position with recesses in the base plate accommodating the electrical components on the circuit board.
U.S. Pat. No. 4,810,048 to Asano et al., describes a plastic or resin material which is molded to form a chassis which incorporates electrical wiring and conductors necessary to operate the electromechanical components mounted onto the chassis. When electrical conductors are deposited on the surface of the resin structure, they may be encapsulated with an insulating layer of material.
U.S. Pat. No. 4,825,316 to Kishi et al., shows and describes a structure wherein an electronic circuit board is at least partially engaged in face-to-face relationship with a sheet metal base place upon which the head transport mechanism is mounted and which also supports the spindle drive motor and spindle.
U.S. Pat. No. 4,930,029 to Morita illustrates a stacked arrangement wherein the electronic circuit board is mounted in a face-to-face relationship with the base or base plate which in turn supports the actuator mechanism and the spindle and spindle drive motor.
Utilizing two separate and stacked elements, the base plate and the electronic circuit board, causes valuable height to be sacrificed.
It is an object of this invention to maintain a rigid spatial relationship between the actuator mechanism and the disk drive spindle while eliminating cumulative height through the use of a hybrid plate.
It is a further object of this invention to reduce the affects of temperature within the disk drive housing and the resultant possible warping and deflection of the base plate.
A further object of this invention is to minimize the temperature rise within the disk drive assembly.
It is still another object of the invention to minimize contamination from the electronic components within the disk drive assembly.